The chemistry of silicon surfaces in aqueous fluoride solutions is complex
and exhibits many unique features. The etch rate of the hydrogen-passivated
surface passes through a maximum at about pH 7 and is slow at low and high
pH. The density of etching intermediates exhibits a sigmoidal behavior of
low density in acidic and high density in basic solutions. Pie show that th
e pH dependence of both the etch rate and the density of intermediates can
be explained by taking into account the fluoride ion concentration, and the
concentrations of molecular HF, the dimer (HF)(2), HF2- as well as OH- and
H2O. (C) 2000 The Electrochemical Society. S0013-4651(99)12-073-1. All rig
hts reserved.